The present invention relates to a photopolymerizable composition and particularly to a composition comprising a mixture of epoxy-containing materials and polymerizable monomers containing one or more ##STR2## groups wherein R is hydrogen or --CH.sub.3. More particularly the present invention relates to a photopolymerizable composition containing in addition to a polymerizable epoxy containing material and a polymerizable monomer, as defined above, an effective amount of a cationic photo-initiator, an effective amount of a radical-type photoinitiator and an alcohol accelerator.
Heretofore, photocurable epoxy-containing materials have been photopolymerized in the presence of a diaryliodonium complex salt photoinitiator and/or a triaryl sulfonium complex salt upon exposure to a source of radiation emitting actinic radiation in the ultraviolet region of the spectrum.
It has also been known to photopolymerize ethylenically unsaturated compounds in the presence of free radical photoinitiators on exposure to visible light and ultraviolet radiation.
Recently, in U.S. Pat. No. 4,156,035 to Tsao et al, there is disclosed a radiation curable composition containing a mixture of epoxy resin and di- or polyacrylate or methacrylate terminated monomers in combination with a catalyst system comprising a carbonyl type photoinitiator with an aromatic onium salt capable of effecting the cure by release of a Lewis acid.
While known all di- or polyacrylate or methacrylate and all epoxy resin systems have certain advantages, such systems often suffer from certain significant disadvantages which prevent their use in some practical applications. For instance, it is known that these homogeneous systems often require ultraviolet radiation to cure the same and exposure to sunlight alone fails to provide an acceptable cure in terms of a sufficiently short cure time as well as in terms of an essentially tack-free condition within an acceptable short cure time. Also it is known that di- or polyacrylate or methactylate systems are often air inhibited and require a nitrogen blanket or other inert atmosphere in order to cure tack-free.